1. Field of the Invention
The present invention relates to an antenna which is used for a radio communication device such as GPS (Global Positioning System) using a frequency band over UHF (Ultra High Frequency), and mounting of the antenna. Along with a surface mounting construction of the antenna, the present invention relates to an antenna element which realizes the improvement of mounting efficiency of mounted components, a mounting method of the antenna element, a plane antenna, and a circuit base board and an electronic device having the plane antenna.
2. Description of the Related Art
Recently, as a mobile communication terminal device, a device which uses a plurality of radio communication methods in one terminal device is becoming widespread. In this case, if each communication method uses different radio communication frequency, it is necessary to provide a plurality of antennas. For example, in a mobile phone unit having a GPS function which receives an electric wave from a satellite and can obtain the information of a present position, since the frequency of a GPS signal is 1.57 GHz, this is different from 800 MHz zone and 2 GHz zone which are frequency bands used by a domestic mobile phone unit in Japan. Because of this, an exclusive antenna for GPS is mounted in addition to an antenna for the mobile phone unit. In this case, when installing a wireless LAN function such as short distance radio communication of 2.4 GHz zone in ISM band, it is necessary to mount an exclusive antenna.
Further, a mobile phone unit and so on is directed to higher development of functions, for example, the embarkation of a digital camera and the addition of a high-speed CPU for the improvement of high-speed processing of software. In addition to this, for example, a liquid crystal display is made bigger. By these, the number of components is increasing and the density of mounted components is becoming higher. Hence, these give restriction to the mounting of a radio communication antenna.
By the way, if a structural element has resonated with a predetermined frequency, the gain of an antenna is improved in proportion as its physical shape becomes larger, and an electrical characteristic of the antenna becomes advantageous. Therefore, when giving precedence to performance, its shape must be made larger. Because of this, in case that an antenna is mounted in a mobile phone unit, a trade-off between a restricted mounting space and an antenna performance satisfying the system gain of a radio communication system is performed. However, since an antenna with predetermined gain is required in order to obtain the minimum system gain, its shape and dimension are naturally decided.
In a GPS antenna receiving a satellite electric wave, since the increment in a receiving level has influence on positioning accuracy, its gain had better be higher. Further, the satellite electric wave is a circularly polarized wave method, and the plane antenna for a circularly polarized wave is required in order to receive its electric wave with higher efficiency.
For example, in a car navigation system, an antenna having a shape of 25 mm square is used. On the other hand, as an antenna for a mobile phone unit use, an antenna of 13 mm square is developed. This shortens electrical length by increasing the specific inductive capacity of a dielectric part and making GPS frequency resonate, and thereby a physical shape is made smaller. However, in this case, its gain falls by a dielectric loss. In case that a miniaturized exclusive antenna for GPS is mounted in a mobile phone unit, since its shape and measure are larger as compared with other parts, a mounting space for the antenna is needed. Obtaining an antenna mounting space like this becomes a cause leading to a fall of an article power in commerce because of an obstructive factor of miniaturization of a mobile phone unit, a restriction of a design of an appearance, and so on.
Like this, in a communication device having an exclusive antenna corresponding to a plurality of radio communication methods, the maintenance of radio communication performance, the improvement of mounting efficiency by means of the improvement of high density of components mounted on a device, the improvement of a multi-function and the miniaturization of a device are requested.
Further, a plane antenna is also called a patch antenna or a micro-strip antenna, and is widely used as a receiving antenna of GPS and so on. For example, a conventional plane antenna has a shape shown in FIG. 1 and FIG. 2. FIG. 1 shows a plan view of the plane antenna, and FIG. 2 shows a sectional view taken along line II—II of FIG. 1. In this plane antenna, for example, a circular antenna pattern part 4 is provided on an upper face of a rectangular dielectric substrate 2, and thereby an antenna element 6 is constructed. A junction conductor 10 is connected to a feeding point 8 of the antenna pattern part 4 by solder 12, and the junction conductor 10 is passed through an inside of the antenna element 6 and is protruded like a pin shape from a back face of the dielectric substrate 2. In a printed circuit base board 14 for mounting the antenna element 6, a ground pattern part 16 is provided, and a through hole 18 is also formed at a position at which the antenna element 6 is arranged. Further, the junction conductor 10 is provided through the through hole 18 of the printed circuit base board 14, and a transmission line 20 as a feeding line is electrically connected to a pointed end portion of the junction conductor 10, which protrudes to the back face side of the printed circuit base board 14, by solder 22. A reference numeral 24 is a connected portion of the junction conductor 10 and the transmission line 20 by means of the solder 22.
Further, FIG. 3 is an outline view showing a conventional GPS receiving module having the plane antenna from an upper face side thereof. On the printed circuit base board 14 as a circuit base board of this GPS receiving module 26, a plane antenna 28, a down converter part 30 which frequency-converts a GPS signal from RF frequency to intermediate frequency (IF), and a position computation signal output terminal part 32 which outputs position information to an outside of the GPS receiving module 26 are mounted.
FIG. 4 is a sectional view taken along line IV—IV of FIG. 3, and FIG. 5 is an outline view showing the GPS receiving module 26 from a back face side thereof. For this GPS receiving module 26, a component mounting part is formed inside a shielding cover 34 which is provided to the back space side of the printed circuit base board 14, and a GPS signal operation processing part 36 performing position computing operation by the signal processing of IF signal and a clock signal generation part 38 are provided therein.
In order to make it possible to receive the electromagnetic wave of a circularly polarized wave with high efficiency as a GPS antenna, the plane antenna 28 is a patch antenna in which the patch-shaped antenna element 6 is formed on a plane. For the plane antenna 28, the antenna pattern part 4 is formed on the dielectric substrate 2 as a surface electrode which is formed on the surface of dielectric by metalizing a conductive material serving as a structural element resonating with predetermined frequency. A circularly polarized wave is composed by making two polarized waves meet at right angles and forming vertically-polarized wave component and horizontally-polarized wave component. The antenna pattern part 4 which is a patch antenna electrode resonates with λ/2 (at this, λ: wave length) in a longitudinal direction. Because of this, if a power source is supplied to a center of the square electrode, in the plane antenna 28 shown in FIG. 3, electromagnetic waves are excited in a longitudinal direction and a transversal direction, and the signal of a circularly polarized wave can be received by the electromagnetic waves meeting at right angles being composed at resonance frequency.
This plane antenna 28 is constructed by the dielectric substrate 2, the antenna pattern part 4 composed of a metalized electrode, and the junction conductor 10 which is a feeding pin, and the antenna becomes a finished product of the plane antenna 28 by connecting between the antenna pattern part 4 and the junction conductor 10 by the solder 12. As described before, by the dielectric substrate 2 and the antenna pattern part 4, the antenna element 6 is constructed.
A mounting construction and method of this plane antenna 28 are explained by referring to FIG. 3 to FIG. 5. In the printed circuit base board 14, a hole piercing to its surface and back face is formed near the center of a portion mounting the plane antenna 28, the plane antenna 28 is constructed by unifying the dielectric substrate 2 and the junction conductor 10, and the junction conductor 10 of the plane antenna 28 is passed through the hole of the printed circuit base board 14. Further, as shown in FIG. 5, a feed connection land 40 existing at the back face of the printed circuit base board 14 and the junction conductor 10 are connected by solder 42. By this, a GPS received signal is led to the down converter part 30 through the transmission line 20 serving as a RF signal transmission line, a down converter part connection land 44 and a down converter part connection through hole 46.
The down converter part 30 performs frequency conversion from the GPS signal (frequency 1575.42 MHz) to the IF signal of 1–100 MHz, and performs position computation through operation processing of the received GPS signal by using the signal processing of a DSP (Digital Signal Processor) in the GPS signal operation processing part 36. And an output result of that position computation is output from the position computation signal output terminal part 32. An output signal given to the position computation signal output terminal part 32 is utilized for the confirmation of position information obtained by the GPS signal. For example, the output signal is given to another device not shown in the drawings and is used for the display of a computed result, or the output signal is transmitted to a personal computer not shown in the drawings and is used for plotting on a map.
As prior patent documents of a plane antenna like this, there are the Japanese Patent Laid Open Publications No. 2000-49526, No. 9-199940 and so on.
The Publication No. 2000-49526 relates to a plane antenna, and discloses that, in order to prevent the generated gas at the time of soldering from being confined in an electrode part and to make stable and firm mounting possible, a groove for leading the gas to an outside is formed in the side of a mounting face of a dielectric substrate.
Further, the Publication No. 9-199940 relates to an electronic circuit device having a plane antenna, and discloses that the plane antenna is provided on a printed circuit base board of the electronic circuit device.
By the way, in case of mounting the plane antenna 28 of a construction like this, as shown in FIG. 6 and FIG. 7, since the plane antenna 28 has a construction in which the junction conductor 10 piercing the dielectric substrate 2 protrudes from a bottom face of the dielectric substrate 2, the junction conductor 10 piercing a hole made in the printed circuit base board 14 on which the plane antenna 28 is provided must be connected to the feed connection land 40 existing on a face opposite to a face on which the antenna is mounted. For example, when setting all over the back face side of the plane antenna 28 to ground potential (GND) against the antenna pattern part 4, the antenna pattern part 4 is set to the shape and dimension resonating with the frequency of 1.57 GHz. In this case, feed must be performed at a center of the antenna pattern part 4. For feeding at the center, a pin for supplying a signal in a vertical direction from a surface portion of the antenna pattern part 4, namely the junction conductor 10 must be provided. In a construction having the junction conductor 10 mentioned above, as shown in FIG. 5, in order to take out a received signal from the junction conductor 10, the junction conductor 10 and the transmission line 20 of the printed circuit base board 14 are connected by punching a hole in the printed circuit base board 14 at a face opposite to a face having the antenna. In a mounting construction like this, since a connecting terminal of the junction conductor 10 occupies a component mounting part of the printed circuit base board 14, other components can not be provided in a circumferential portion of the feed connection land 40 to which the junction conductor 10 is connected.
Because of this, in case of mounting the plane antenna 28 on a printed circuit base board of a mobile phone unit, a part of a face opposite to a mounting face is occupied by the feed connection land 40, and moreover, the junction conductor 10 piercing the printed circuit base board protrudes to a back face side of the printed circuit base board and becomes a protruding portion. Because of this, there is a problem that these prevent other components from mounting.
That is, in a receiving device in which the plane antenna 28 is provided, in order to lead a signal received by the antenna pattern part 4 to a low-noise amplifier and a down converter circuit, the transmission line 20 is provided in the back face side of the printed circuit base board 14, and this transmission line 20 and the junction conductor 10 protruding to the back face side of the printed circuit base board 14 are connected by the solder 22 (FIG. 2). Because of this, on the rear face side of the printed circuit base board 14 to which the connected portion 24 and the transmission line 20 are exposed, mounting other components and arranging a component closely to the printed circuit base board 14 becomes difficult. Hence, there is an inconvenience that the mounting of the plane antenna 28 and the arrangement of components are restricted.
In case that the printed circuit base board 14 is thin, the junction conductor 10 protrudes to the back face side of the printed circuit base board 14, and, if this protruding length is long, the mounting of components and so on which adhere closely to the back face of the printed circuit base board 14 becomes impossible. Because of this, the mounting efficiency of components to the printed circuit base board 14 is to lower. Further, in the mounting construction in which the junction conductor 10 is made to pierce, it is necessary to form the through hole 18 in the printed circuit base board 14, and a pattern design considering the through hole 18 also becomes necessary in respect to the printed circuit base board 14.
Further, since the connected portion (the solder 12) of the side of the feeding point 8 and the connected portion 24 (the solder 22) of the side of the transmission line 20 exist respectively on different faces of the printed circuit base board 14, there is an inconvenience that these connections must be treated with separate processes. Furthermore, in a shape having the junction conductor 10 and its connected potion 24 exposed to the back face side of the printed circuit base board 14 through the ground pattern part 16, there is an inconvenience that noise strength is low because of being liable to accept the influence of a noise from the back face of the printed circuit base board 14 toward the feeding point 8 and so on.
The mounting construction of a plane antenna toward a circuit base board for a mobile phone is explained by referring to FIG. 8. FIG. 8 is a side view showing the mounting construction of the plane antenna of the mobile phone circuit base board. On this mobile phone circuit base board 48, a key input part 50, which is an information input part, and an information display part 52 are provided. The plane antenna 28 has a construction in which the junction conductor 10 protrudes from the bottom face of the dielectric substrate 2. Because of this, in the mobile phone circuit base board 48 on which this plane antenna 28 is mounted, other components must be provided so as to avoid the junction conductor 10 protruding from a back face of that base board, and besides, a feed connection land for connecting to the junction conductor 10 is required, for example. Hence, these become a cause making amounting area for components of the mobile phone circuit base board 48 enlarge.
In the printed circuit base board having the plane antenna as mentioned above, the connected portion of the plane antenna occupies up to the mounting region of its back face side, that prevents the printed circuit base board from the improvement of its reduction, and the fall of mounting density of components and the fall of mounting efficiency occur. As a result, these become a cause preventing a device having the plane antenna, such as a mobile phone, from its miniaturization.
The problems mentioned above are not disclosed in the Publications No. 2000-49526 and No. 9-199940, and can not be solved even if technology disclosed in these patent documents is used.